The invention relates to an adjusting device for varying the inclination of a steering column of a motor vehicle of the type which controls a pivoting movement of the steering column about a pivot bearing arranged remotely from a steering wheel at a lower region of the steering column. The movement of the steering column can be effected by an adjusting mechanism which acts in a straight line in the direction of the inclination adjustment and which is connected to a casing tube accommodating the steering column in an upper region of the steering column near the steering wheel, whereby the steering column can be braced against the vehicle body in this upper region, and wherein a sliding stroke of this connection relative to the vehicle body which is dictated by the pivoting movement is permitted bY a guide lever mounted articulately to the vehicle body and acting articulately relative to the steering column.
An adjusting device of this general type is described in DE-PS 3,536,285. According to the latter a steering column, which is pivotable about an end pivot bearing and which is accommodated by a casing tube surrounding it, is variable in inclination by an adjusting mechanism connected to the casing tube in a region near the steering wheel and acting in a straight line. This adjusting mechanism also braces the steering column against the vehicle body in this upper region. The upper bracing is particularly important for the load capacity of the steering column when a force is introduced into the steering wheel, for its low vibration mounting and for a definite deformation resistance when impact forces are introduced into an impact absorber connected to the steering wheel during an accident.
However, the problem arises with this bracing arrangement that the connection of the adjusting mechanism and casing tube travels a sliding stroke relative to the vehicle body which is dictated by the pivoting movement about the pivot bearing remote from the steering wheel, so that the adjusting mechanism cannot simply be connected rigidly to the casing tube and to the vehicle body but that a steering or guiding lever which permits this sliding must be provided In the above-mentioned German patent this guide lever function is associated with the adjusting mechanism, which has to be fastened articulately at both ends and constructed adjustably in its adjusting movement for this purpose. The entire adjusting mechanism changes its position relative to the casing tube and to the vehicle body continuously, so that the attachment of a motor and gear to drive the adjusting mechanism necessitates additional means which are intended to permit either a stable mounting on the moving adjusting mechanism, or a flexible drive connection.
An underlying object of the invention is to achieve a compact, stable construction and a favorable attachment of a drive means to the adjusting mechanism for an adjusting device of the type described above.
This object is achieved by providing an arrangement wherein a rectangular frame surrounds the casing tube with the inside cross-section of the rectangular frame being fastened to the vehicle body by a frame body wall located transversely to the direction of the inclination adjustment, the side walls of said rectangular frame located at right angles to this body wall serving as guide levers which are connected for this purpose by their end sections to the frame body wall and to a frame bearing wall opposite the frame body wall pivotably in their plane relative to the frame body wall, and wherein the adjusting mechanism, which is mounted stationary on the frame bearing wall, exhibits a fixed angular position with respect to the frame bearing wall and to the casing tube.
According to the invention the necessary steering function is completely separated from the adjusting mechanism, which is linearly driven, mounted stationary and effects a precise adjusting stroke in the direction of inclination of the steering column.
The frame surrounds and protects the adjusting mechanism and provides a stable bracing for the adjusting mechanism.
According to further features of preferred embodiments of the invention, the adjusting mechanism comprises two screwthreaded spindles which brace the adjusting force uniformly on both sides of the steering column, and which dictate weak adjusting forces in the case of an alignment at right angles to the longitudinal axis of the casing tube in tangential alignment to the radius of inclination.
The outlay for especially preferred embodiments of the adjusting device is also reduced by the fact that only one of the screwthreaded nuts which initiate the adjusting movement into the casing tube is actuated by a drive means, whereas the other screwthreaded nut is rotatable synchronously through a frictional transmission means, such as, for example, a chain.
According to certain preferred embodiments the screwthreaded spindles exhibit a trapezoidal screwthread and the gear exhibits worm wheels, whereby it is possible to use compact motors with high speed and power, the speed of which is reduced by these measures.